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Fluids
Special Issues
Galactic, Astrophysical and Planetary Dynamos
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Galactic, Astrophysical and Planetary Dynamos

A special issue of Fluids (ISSN 2311-5521).

Deadline for manuscript submissions: closed (31 January 2022) | Viewed by 5486

Special Issue Editor

Prof. Dr. John Shebalin

E-Mail Website
Guest Editor
Department of Physics and Astronomy, George Mason University, Fairfax, VR 22030, USA
Interests: magnetohydrodynamics (MHD); statistical mechanics of MHD turbulence; dynamo theory; astrophysical fluid dynamics; spectral method computation

Special Issue Information

Dear Colleagues,

Large-scale magnetic fields are observed surrounding galaxies, stars, and planets and are thus universal phenomena. These magnetic fields are believed to be due to magnetohydrodynamics (MHD) processes in the energetic, turbulent magnetofluids that lie within these objects. One important characteristic observed is the dominance of a quasi-steady dipole component. It has long been realized that MHD dynamos must exist to create large-scale, i.e., dipole, magnetic fields. A full understanding of the origin and evolution of these large-scale magnetic fields will result in a solution to the “dynamo problem”. Historical approaches to studying these phenomena, such as kinematic dynamo theory and mean-field electrodynamics, have, in general, proven unsatisfactory. For this Special Issue of Fluids, we solicit papers presenting modern approaches to understanding galactic, astrophysical, and planetary dynamos. The focus of these papers may include MHD turbulence, inertial wave effects, mechanisms for forcing and dipole alignment, creation of plasma jets and mass ejections, and other related topics. The MHD dynamos studied may range from those in planets and stars to those in active galactic nuclei, in the galaxy as a whole, and in galaxy clusters, i.e., both non-relativistic and relativistic physical phenomena. Methods of study can include theoretical analysis, statistical mechanics, numerical simulation, and astronomical observation.

Prof. Dr. John Shebalin
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Fluids is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • magnetohydrodynamics
  • turbulence
  • dynamos
  • galaxies
  • stars
  • planets

Published Papers (3 papers)

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Research

7 pages, 241 KiB  
Communication
Can a Dynamo Mechanism Act at the Magnetopauses of Magnetic Rapidly Rotating Exoplanets?
by Elena Belenkaya
Fluids 2022, 7(2), 60; https://doi.org/10.3390/fluids7020060 - 31 Jan 2022
Viewed by 1791
Abstract
An astrophysical dynamo converts the kinetic energy of fluids into magnetic energy. Dynamo is a non-local process. Here, we consider whether a dynamo can operate at the magnetopauses of magnetic rapidly rotating planets. We analyze the main necessary condition for the work of [...] Read more.
An astrophysical dynamo converts the kinetic energy of fluids into magnetic energy. Dynamo is a non-local process. Here, we consider whether a dynamo can operate at the magnetopauses of magnetic rapidly rotating planets. We analyze the main necessary condition for the work of this type of dynamo—the rotation transfer from the planet to the magnetopause. We show the role of the current disc around a rapidly rotating magnetic planet in the redistribution of angular momentum depending on the direction of the external magnetic field, using the example of the Jupiter’s magnetodisc. Full article
(This article belongs to the Special Issue Galactic, Astrophysical and Planetary Dynamos)
23 pages, 3707 KiB  
Article
Inertial Waves in a Rotating Spherical Shell with Homogeneous Boundary Conditions
by John V. Shebalin
Fluids 2022, 7(1), 10; https://doi.org/10.3390/fluids7010010 - 29 Dec 2021
Cited by 1 | Viewed by 1146
Abstract
We find the analytical form of inertial waves in an incompressible, rotating fluid constrained by concentric inner and outer spherical surfaces with homogeneous boundary conditions on the normal components of velocity and vorticity. These fields are represented by Galerkin expansions whose basis consists [...] Read more.
We find the analytical form of inertial waves in an incompressible, rotating fluid constrained by concentric inner and outer spherical surfaces with homogeneous boundary conditions on the normal components of velocity and vorticity. These fields are represented by Galerkin expansions whose basis consists of toroidal and poloidal vector functions, i.e., products and curls of products of spherical Bessel functions and vector spherical harmonics. These vector basis functions also satisfy the Helmholtz equation and this has the benefit of providing each basis function with a well-defined wavenumber. Eigenmodes and associated eigenfrequencies are determined for both the ideal and dissipative cases. These eigenmodes are formed from linear combinations of the Galerkin expansion basis functions. The system is truncated to numerically study inertial wave structure, varying the number of eigenmodes. The largest system considered in detail is a 25 eigenmode system and a graphical depiction is presented of the five lowest dissipation eigenmodes, all of which are non-oscillatory. These results may be useful in understanding data produced by numerical simulations of fluid and magnetofluid turbulence in a spherical shell that use a Galerkin, toroidal–poloidal basis as well as qualitative features of liquids confined by a spherical shell. Full article
(This article belongs to the Special Issue Galactic, Astrophysical and Planetary Dynamos)
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9 pages, 321 KiB  
Article
Mantle Electrical Conductivity and the Magnetic Field at the Core–Mantle Boundary
by John V. Shebalin
Fluids 2021, 6(11), 403; https://doi.org/10.3390/fluids6110403 - 8 Nov 2021
Cited by 2 | Viewed by 2032
Abstract
The Earth’s magnetic field is measured on and above the crust, while the turbulent dynamo in the outer core produces magnetic field values at the core–mantle boundary (CMB). The connection between the two sets of values is usually assumed to be independent of [...] Read more.
The Earth’s magnetic field is measured on and above the crust, while the turbulent dynamo in the outer core produces magnetic field values at the core–mantle boundary (CMB). The connection between the two sets of values is usually assumed to be independent of the electrical conductivity in the mantle. However, the turbulent magnetofluid in the Earth’s outer core produces a time-varying magnetic field that must induce currents in the lower mantle as it emerges, since the mantle is observed to be electrically conductive. Here, we develop a model to assess the possible effects of mantle electrical conductivity on the magnetic field values at the CMB. This model uses a new method for mapping the geomagnetic field from the Earth’s surface to the CMB. Since numerical and theoretical results suggest that the turbulent magnetic field in the outer core as it approaches the CMB is mostly parallel to this boundary, we assume that this property exists and set the normal component of the model magnetic field to zero at the CMB. This leads to a modification of the Mauersberger–Lowes spectrum at the CMB so that it is no longer flat, i.e., the modified spectrum depends on mantle conductance. We examined several cases in which mantle conductance ranges from low to high in order to gauge how CMB magnetic field strength and mantle ohmic heat generation may vary. Full article
(This article belongs to the Special Issue Galactic, Astrophysical and Planetary Dynamos)
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